What version of Videopad? Clear Unused Cache Files, under OPTIONS|DISK. Be sure that the hard drive has ample free space.
Try an install of the latest release.
If you are a registered user, remember that upgrades are free for up to six months. After that, your purchase will continue to fully function but a fee will be required in order to register the latest. Always retain the installer file, though it's automatically backed up on the PC.
If it still fails, try a clean uninstall, using this tool. Then reinstall Videopad. Report results here.